THE number of transistors that can be put on a computer chip tends to double about every two years, just as Intel Corp.'s co-founder Gordon Moore predicted more than 20 years ago. But lately, experts have been worried that Mr. Moore's law might falter as the laws of physics catch up with the ability to cram more and more on a chip. That's why Lawrence Livermore--with its skills in optics, precision machining, multilayer coatings, miniaturization, and a host of other capabilities developed in its weapons work--teamed up with fellow DOE laboratories Lawrence Berkeley and Sandia to literally shed new light on the subject. They also teamed up with three of the biggest names in the semiconductor industry--Intel, Motorola, and Advanced Micro Devices. The result is a $250-million project, funded by corporate money, to continue developing extreme ultraviolet (EUV) lithography technology.|
The team's strategy has been to focus on specific technologies for EUV lithography, including multilayer coatings, projection optics, optical substrates, mask and optical design, and metrology (Figure 1). Livermore brings expertise in optics, precision engineering, and multilayer coatings; Sandia's part includes the systems engineering, the resists (protective coatings that prevent unwanted etching), and the light source. Berkeley provides its Advanced Light Source to characterize the optics and resists in the EUV range.
Traditionally, advances in optical lithography--a photography-like technique of using light to carve channels on silicon wafers--have relied on using shorter and shorter wavelengths of light, which can produce smaller features much as a razor can make a finer cut than a hacksaw. State-of-the-art techniques use ultraviolet (UV) light, and experts believe that chips will continue to follow Moore's law for another 10 years as even shorter wavelengths are used.
Current systems use UV light with a wavelength of 0.248 micrometer, to image a master pattern through lenses onto a silicon wafer that is covered by a resist. This technology can produce features of just 0.25 micrometer, or about one four-hundredth the width of a human hair. In less than 10 years, engineers plan to build chips with features measuring about 0.13 micrometer by using wavelengths of 0.193 micrometer. But beyond that point, physics intervenes and light shorter than that--called extreme ultraviolet light--will be absorbed, rather than refracted, by a conventional quartz lens. The result: no image.
Enter Multilayer Coatings
The Incredible Shrinking Chip
Why are smaller computer chips better and faster? It might seem a paradox, but as the size decreases, the chips become more powerful. It's as simple as getting to grandma's house faster if she lives next door rather than across town: the electronic signals zipping around the circuitry to solve computing problems have less distance to travel. Today's chip contains about 3,260 times more transistors than the chip of 1971. Here's a chronology of the shrinking of chips as the semiconductor industry became a $150-billion enterprise.
Boosting EUV Lithography
Key Words: Absolute Interferometer, Advanced Microtechnology Program, extreme ultraviolet (EUV) lithography, Ultra Clean Ion Beam Sputter Deposition System.
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